Control system



CONTROL SYSTEM 7 Sheets-Sheet 1 Filed Oct. 6, 1952 mwN www J ATTORNEY.

CONTROL SYSTEM Filed Oct. 6, 1952 7 Sheets-Sheet 2 A TTORNE Y.

CONTROL SYSTEM 7 Sheets-Sheet 3 Filed OCL. 6, 1952 INVENTORS ATTORNEY.

Dec. 13, 1955 Filed Oct. 6, 1952 Ill R. A. MERRILL ETAL 2,726,922

CONTROL SYSTEM 7 Sheets-Sheet 4 ATTORNEY,

Dec. 13, 1955 R. A. MERRILL ETAL CONTROL SYSTEM 7 Sheets-Sheet 5 FiledOct. 6, 1952 ATTORNEY.

Dec. 13, 1955 R. A. MERRILL ETAL 2,725,922

CONTROL SYSTEM Filed Oct. 6, 1952 7 Sheets-Sheet 6 IIIIIHIIN A TTORNE Y.

CONTROL SYSTEM Filed oct. 6, 1952 L-ll ATTORNEY.

Uni@ Statement O CONTROL SYSTEM Robert A. Merrill, Detroit, and Henry S.Mika, Birmingham, Mich., assignors to United States Rubber Company, NewYork, N. Y., a corporation of New Jersey Application October 6, 1952,Serial No. 313,282

Claims. (Cl. 18-2) This invention relates to a control system for aseries of conveyors used in conveying continuously extruded plasticmaterial from an extruding die to a severing mechanism.

It is common practice in conveyor installations of this type to make theconveying system of considerable length to allow the freshly extrudedmaterial to cool and set before it reaches the severing mechanism whereit is cut into short predetermined lengths. It is also common practiceto include cooling baths in a line of separate conveyors to increase therate of cooling.

When the plastic material is extruded, the material is quite soft andthe speed of the immediate take-away conveyor which carries the materialfrom the die determines the weight of the stock per unit of length. Ifthe speed of the take-away conveyor is increased, the weight of thematerial per unit of length will be decreased because it is stretched bythe conveyor as it is pulled from the extruding die` It is thereforenecessary in controlling the weight of the extruded material toaccurately control the speed of the take-away conveyor. It is oneobject, therefore, of the present invention to provide a mechanism forcontinuously weighing the extruded material and a control system forincreasing or decreasing the speed of the conveyors in the event thatthe weight of the material varies from a predetermined desired standardWeight.

As the material is transported by the series of conveyors through thevarious baths, it is cooled and in cooling undergoes considerableshrinkage. if all the conveyors in the series are operated at the samespeed, then the conveyors remote from the extruding die will beoperating at a linear speed greater than that at which the material isbeing supplied to them and they will stretch the material therebyinducing tensile stresses into the material or they may actuallypermanently stretch the material. If the material is under tensilestress when it reaches the severing mechanism, it is impossible to cutthe material accurately to a predetermined length because when it is cutand removed, it will retract to a shorter length due to these tensilestresses. Because of the unpredictable nature of plastic materials, andin particular rubber, it is impossible to predict the amount ofshrinkage, so that a correction factor can be applied in cutting thematerial. It is a further object, therefore, of the present invention toprovide a control system which will continuously measure the tension ofthe material at a plurality of points along the conveyor line andincrease or decrease the linear speed of the individual conveyors tomaintain the material at a predetermined desired tension throughout itstravel.

In addition to being able to accurately cut the material topredetermined lengths, it is also important that these lengths be of apredetermined weight. Because of the unpredictable amount of shrinkagein the material in its travel to the severing mechanism, it isimpossible to predetermine accurately what the change of weight per unitof linear measurement of the stock will be due to this shrinkage.However, the shrinkage will be proportional to the difference in speedof the iirst and last conveyors, if the conveyors are operated at speedsthat will maintain the material at substantially zero tension. It is,therefore, a still further object of the present invention to provide acontrol system which will utilize this difference in speed of the firstand last conveyors in applying a compensating factor in the weightcontrol system so that the cut lengths will be of the desired standardweight.

It is a still further object of the present invention to provide anintegrated control system for a series of conveyors used in conveyingcontinuously extruded plastic material, such as rubber, from anextruding die to a severing mechanism, which will accurately andautomatically control the weight of and the tension in the extrudedmaterial and will apply a factor to compensate for the Weight change dueto shrinkage during the movement of the extruded material from theextruding die to the severing mechanism, so that lengths severed fromthe material will be of a desired length and weight.

A still further object of the invention is to provide an integratedcontrol system for a series of conveyors used in conveying continuouslyextruded rubber tread stock for pneumatic tires from an extruding diecommonly known as a tubing mill to a severing mechanism; which controlsystem will acurately and automatically control the weight of and thetension in the tread stock and will apply a factor to compensate for theweight change due to shrinkage during the movement of the tread stockfrom the tubing mill to the severing mechanism, so that lengths severedfrom the continuous strip of stock will be of uniform length and weight.

Gther objects and advantages of the present invention will becomeapparent from the following description when read in conjunction withthe accompanying drawings; wherein TEig. l is a schematic drawing of atypical conveyor vsystem for extruded plastic material to which thecontrol system of the present invention may be applied, the drawingshowing the location of the mechanical elements including the continuousweighing scale, the scale cornpensating mechanism, the conveyor motors,the tachometer generators, and the control selsyn transmitters of thecontrol system of the present invention;

Fig. 2 is an elevational view showing the mechanical features of thecontinuous weighing scale and scale compensating mechanism;

Fig. 3 is a view taken on line lli-lll of Fig. 2 show.- ing themechanical details of the scale compensating mechanism;

Fig. 4 is an elementary wiring diagram showing a portion of theelectrical circuit of the control system;

Fig. 5 is a continuation of the electrical diagram of Fig. 4;

Fig. 6 is a continuation of the electrical diagram of Fig. 5; A

Fig. 7 is a plan view of a variable speed drive used in modifying thecontrol system for use with A. C. constant speed conveyor motors.

Fig. 8 is a schematic drawing showing how variable speed drives of thetype shown in Fig. 7 can be incorporated in the control system, so thatA. C. constant speed conveyor motors can be utilized; and

Fig. 9 is an elementary wiring diagram showing a modiiication of thediagram of Fig. 6.

Referring to Fig. l of the drawings, there is shown a typical conveyorsystem for conveying an extruded strip lil of plastic material, such asrubber, from an extruding die l1 to a severing mechanism i2. in theparticular system shown, there are four individual belt conveyorsdesignated as 13, 14, 15 and 16 and one conveyor roller designated as18.

The conveyor system shown is of a type commonly used in the extrusion ofrubber tread stock for pneumatic tires commonly known as tubing." Thecontrol system of the present invention which will hereinafter bedescribed is particularly useful in the extruding of such stock as itwill accurately control the weight of the stock per unit of length, anddeliver the stock to the severing mechanism at substantially zerotension so that the stock may be accurately cut into sections oftermined length and weight. In the manufacture of tires the tread stockis wrapped around the tire carcass while it is on a tire building drumand if the tread stock is not of the proper length, it is necessary toeither trim the stock if it is too long or stretch the stock if it isloo short in order to tit it to the drum. These extra operations areeliminated by the present invention, inasmuch as the stock may beaccurately cut to the proper length and weight.

Between conveyor 14 and roller 1S there is a cooling tank 19 and betweenroller 13 and conveyor 15 there is a second cooling tank 20. A coolingliquid, such as water, is circulated in the tank 19 and 20 to acceleratethe rate of cooling of the extruded strip as it is passed therethrough.

Conveyors 13 and 14 are spaced apart suliiciently to accommodate betweenthem a continuous weighing scae 21 and a scale compensating mechanism22, as will be later described. Conveyor 14 is driven from, and at thesame speed as, conveyor 13 by a chain drive 23. Conveyor 13 is driven bya D. C. motor M-ll. The conveyor roller 1S is driven by a D. C. motorifi-2, conveyor Y15 by a D. C. motor lvl-3, and conveyor 16 by a D. C.motor M-4.

The control system for the series of conveyors, for the purpose otexplanation, may be divided into three headings which may be entitledaccording to their primary functions as, Weight control, Loop or Tensioncontrol, and Scale compensator. These divisions of the combinationcontrol system will be described undothese headings and in the ordergive l Weight control The weight control includes a continuous weighingscale 21, schematically shown in Fig. l and in detail in Figs. 2 and 3.

Referring to Fig. 2, the scale 21 includes a supporting frame 24, afulcrum 25, and a balance beam 25 pivoted on the fulcrum 2S. A slidablecounter-balancing weight 27 is carried by a scale 223 secured to the topof the balance beam 26. A harness 29 is pivotaliy secured to the beam 26and carries a roller 30 at its free end. The roller 30 is positioned atthe geometric center between two supporting rollers 31 and 32. Thespacing between the rollers 31 and 32 is adjustable as will be laterbrought out in the description of the scale compensating system.

The strip of extruded material 1G passes from the conveyor 13 over thesupporting rollers 31, over scale roller 30, over supporting roller 32onto conveyor 14. Sliding weight 27 is adjusted to balance the scale atthe desired weight per unit length of the strip of material. lt thematerial is heavier than the desired weight then the strip of materialbetween the two supporting rollers resting on the scale roller 30 willdeflect the balance beam downwardly and if the material is lighter thandesired, the balance beam will move upwardly.

The free end of the balance beam is attached to a movable iron core 33of a diterential type transformer 34. The transformer 34 has twosecondary windings. When the iron core 33 is in the geometric center ofthe transformer, the induced voltages in the two secondary windings areequal but opposed so that there is no voltage output. If the iron coreis moved up or down away from the geometric center of the transformer bythe balance beam .2.6, thereby indiening a dsviatisn from the 1@- siredweight, the voltage output of the secondary windings will beproportionateto the distance the core is moved from the geometric centerand therefore the deviation from standard weight of the strip 10; andthe instantaneous polarity of the output voltage will depend on thedirection of movement Vof the iron core.

In broad terms, the weight control circuit takes the voltage output fromthe transformer 34 and feeds it to an amplifying circuit. .The amplifiedvoltage is then applied to drive la servomotor in one direction or theother depending upon the instantaneous polarity of the voltage. Theservomotor drives a slider on a potentiometer which is connected inseries with the eld windings ot' a D. C. generator. `All the' conveyormotors Mal, M-2, M-S and M-4 are D. C. motors and are driven or theoutput of the D. C. generator. When the slider on the potentiometer ismoved, the resistance in the tield circuit of the generator is increasedor decreased, as the case may be, thereby decreasing or increasing theoutput of the direct current generator and the speed of all the conveyormotors. In this manner the speed of the motors is varied in accordancewith the weight deviation from a desired standard of the extrudedmaterial as determined by the movement of the iron core of thetransformer 34. if the speed of the conveyor motors is increased. thecxtruded material is stretched slightly as it leaves the cxtruding die11, thereby decreasing the weight per unit length thereof. If the speedof the conveyor motors is decreased, the weight per unit length of theextruded material is slightly increased.

The weight control circuit is shown in detail in thc diagram of Fig. 4.ln this diagram as well as the other wiring diagrams, all switch'esareshown in their nonactuated position and all solenoids are shown in theirnon-energized condition. Operation of the conveyor sys tcm andenergization of the control circuit is initiated by manually operating`push .button switch 200 which connects three phase, A. C. motor MG witha 440 volt source (not shown) by means of wires L-l, L-2 and L-S. MotorMG drives D. Cfgenerator 201 which in turn supplies direct current todrive `D. C. conveyor motors M-l, M-2, M-3 and M-4 (Fi'gJ 6) ,by meansof feed lines L9 and L-10.

Closing of switch 200 also energizcs the primary winding 202:1 of a stepdown transformer 202. Secondary winding 202!) is connected acrossconductors L-/i, L-S to provide volts A. C. This voltage is furtherreduced to 6 volts for certain of the control circuits by means of atransformer 203. The 6 volts is applied to the primary winding 34a ofthe differential transformer 34. A manually adjustable rheostat 203:1 isprovided in the circuit for the primary winding v34:: for accuratelysetting the voltage. `Transformer 34 has two secondary windings 34b and34e and the movable iron core 33 aitached to the free end of the balancebeam 26 as previously described.

The weight control circuit may be either manuali;- operated as will belater described or automatically operated. Automatic operation 'isinitiated by closing switch 204. Closing switch 204 completes a circuitacross power supply lines L-4 and L45 to energize control relay 205.Energization of control relay 20S opens normally closed contacts 205:1and 205i: in the circuits to the eld windings 206a and 2060 of aservomotor 206 and closes normally open lcontacts 205C and 205:! in theeld windings 207:1 and 207b` of' a servomotor 207.

Closing of switch 204 also energizes control relays 208, 209 and a timer210. Energization of control relay 208 closes normally open contacts203:1 and 208e and opens normally closedcontacts 208b and 208:2. Closingof contacts 208:1 connects a potentiometer 211 in parallel across aresistor 212 through normally closed contacts 218b. Opening of contacts2081? disconnects a potenti ometer 213'fr'orn' across 'the 'resistor`212 Closing' of contact 208e` connects the slider of potentiometer 211with an ampliiier 214. Opening of contacts 208:1 disconnects the sliderof potentiometer 213 from the amplifier 214.

Energization of control relay 209 opens normally closed contacts 209aand 209C and closes normally open contacts 209b. Opening contacts 209ede-energizes a clutch operating solenoid 215a to release a clutch 215which connects servomotor 206 with the slider of potentiometer 213.Closing of contacts 209b connects the slider of a rheostat 216 in theiield circuit 20161 of generator 201. Opening of contacts 209edisconnects a resistor 217 from the field circuit of the generator 201.The field circuit is supplied by a 200 volt D. C. supply source.

Energization of timer 210 closes normally open contacts 210e butinterposes a time delay in the closing of the contacts. This time delayis inserted to permit the extrusion of the material to become stabilizedbefore the automatic weight control takes over. Closing of contacts 210ecompletes a circuit to energize a control relay 218 and clutch operatingsolenoid 219a of a clutch 219, if at the same time microswitch 220 (Fig.5) is also closed. Microswitch 220 is operated by a cam plate 221 whichis driven at a reduced speed by means of a gear set 222 from theconveyor 13. The reduction in speed of the cam plate 221 is such thatmicroswitch 220 will be actuated for about l0 seconds and nonactuatedfor a. period sufiicient in length to allow the extruded material tomove from the extruding die 11 to a point just beyond the weighing scale21.

When contacts 21051 and microswitch 220 are lboth closed, control relay218 and clutch operating solenoid 219e are energized. Energization ofclutch operating solenoid 219a engages clutch 219 to connect servomotorl207 with the slider of potentiometer 216. Solenoid 219a is directcurrent operated, and an appropriate recti fying circuit including aselenium rectifier 223, capaci` tor 224, and resistor 225 is provided.

Energization of control relay 218 closes normally open contact 218a andopens normally closed contacts 212th. Opening of contacts 21Sbdisconnects potentiometer 211 from across resistor 212 and closing ofcontact Zla places it in parallel with the secondary winding 34C oftransformer 34.

During the ten second interval while microswitch 220 is.

closed, the circuit is in condition to take a weight measure,-4

ment and apply a correction to the speed of the conveyors. lf the ironcore 33 is in the geometric center of the transformer 34, there isinduced in the secondary windings- 34b and 34e, equal but opposedvoltages and there is no resultant output voltage and consequently nocorrection is made to the speed of the conveyors. if, however, the ironcore 33 is moved from the geometric center of the transformer 34 by theweighing scale 21, thereby indicating a deviation from standard weight,the voltage induced in the two secondary windings 3411 and 34C will notbe equal. There will, therefore, exist a voltage difference between theslider of potentiometer 211 and the center tap of resistor 212, inasmuchas the potentiometer 211 is connected in parallel across winding 34C andresistor 212 is connected across winding 34h. The difference in voltage,which has an instantaneous polarity depending on the direction ofmovement of the iron core, is fed intothe amplifier 214 by means ofconductors 214:1 and 21411'. Power is supplied to the amplifier by thell() volt supply lines L-4 and L-S. Amplifier 214 is of a conventionaltype well known to those skilled in the art and includes a voltageamplifying stage and a power amplifying stage. A simplified circuitdiagram of the amplifier 214 is in.- cluded in Fig. 4 for the purpose ofillustration. The amplifier' 214 ampliies the signal voltage and feedsit to the tield winding 207a of servomotor 207 through previously closedcontacts 205a' of control relay 205 which was energized on manuallyclosing switch 204. Field 'azzecca 6, winding 207b was connected acrossvolt lines L-4 and L-S by the closing of contacts 205C.

Servomotor 207, as well as servomotor 206, is of the induction type sothat the phase relation between the current in the two field windingsdetermines the direction of rotation of the motor. The phaserelationship between the field winding 20'7a and 207b is determined bythe instantaneous polarity of the signal voltage fed into the amplifier214 by the secondary windings 34h and 34e. The instantaneous polarity ofthe signal voltage in turn is determined. by the direction of movementof the iron core 33. li the core is moved in one direction fromgeometric center, the servomotor will therefore turn in one directionand if the core moves in the opposite direction the servomotor will turnin the opposite direction. As servomotor 207 rotates it moves the sliderof the potentiometer 211, which is connected thereto, an amount torestore electrical balance between it and the center tap of the resistor212. At the same time servomotor 207 moves the slider of potentiometer216 which is connected to the servomotor 207 by means of clutch 219,which had been previously engaged by clutch operating solenoid 219g.

Movement of the slider of potentiometer 216, which had been previouslyinserted in the field circuit of the generator 201 by closing contacts209b and opening contacts 269e of control relay 209, varies theresistance in the eld of the generator 201 and therefore the outputthereof. The variation of the output of generator 201 varies the speedof all the conveyor motors connected across lines L-9 and L-10, so thatthey will operate at the proper speed to give the desired weight andreturn the balance beam 2d of the weighing scale 21 back to the Acenterof the scale.

When microswitch 220 is released, control relay 213 and clutch operatingsolenoid 21911 are de-energized- V/hen control relay 21S isde-energized, contacts 2135i open and contacts 218b close. This connectspotentiometer 211 in parallel with resistor 212 across the secondarywinding 3419 of transformer 34. As so connected, there will be a voltagedifference between the slider of potentiometer 211 and the center tap ofthe resistor 212, inasmuch as the slider of potentiometer 211 had beenpreviously moved by the servomotor 207. This voltage diterence is fedinto the ampliiier 214 and as amplied it drives servomotor 207 to resetslider of the potentiometer 211 to the center of the range so that therewill be electrical balance between it and the center tap of the resistor212. The slider of potentiometer 216 does not move at this time becauseclutch 219 was de-energized when the clutch operating solenoid 219:1 wasde-energized by the release of microswitch 220.

When microswitch 22d is again operated by cam plate 221, the cycie ofweight measuring and correction is again repeated automatically it thisis necessary as reflected by the position of the iron core 33 of thetransformer 34.

if it is desired to control the weight of the extruded materialmanually, switch 204 is opened thereby deenergizing control relays 205,20S, 209 and timer 210.

De-energization of control relay 205 opens contacts 2i5d and 265C todisconnect the field winding 207:1 and 2071: of servomotor 207, andcloses contacts 205a and 205b to connect the field winding 206a ofservomotor 2do to the amplifier 214 and 206b ield windings across 110volt lines L4 and L-5.

De-energization of control relay 208 opens contacts 203e and 2niteand'closes contacts 20817 and 208:1. Opening of contacts 208edisconnects the slider of potentiometer 211 from the amplifier 214 andclosing of contacts 26Std connects the slider of the potentiometer 213to the amplifier 214. Opening of contacts 208g disconnects potentiometer211 from across the resistor 212 and closing contacts 208b connects thepotentiometer 213 in parallel across the resistor 212.

De-energization of control relay 209 closes contacts 20911 and 209C andopens contacts 20911. Opening of contacts 209b disconnects potentiometer216 from the field circuit of generator 201 and closing of contacts 209Cconnects resistor 217 in series with the field circuit of generator 201.Closing of contacts 20911 energizes clutch operating solenoid 21511 toengage clutch 215. Solenoid 21551 is direct current operated and anappropriate rectifying circuit including a selenium rectifier 226,resistor 227 and capacitor 228 is provided.

De-energization of timer 210 opens contacts 21051. Opening of contacts21051 de-energizes control relay 2115 and the clutch operating solenoid21911. De-energization of control relay 218 opens contacts 21011 andcloses contacts 21817. Opening of contacts 21851 disconnectspotentiometer 211 from across the secondary winding 345q of thetransformer 34. Closing of contacts 210.5 wonlri ordinarily connectpotentiometer 211 across the resistor 212 but does not do so becausecontacts 20511.'. are open at this time. De-energization of clutchoperating solenoid 21951 releases clutch 219 to disconnect Servomotorl207 from the slider of potentiometer 216.

The speed of the conveyor motorsand therefore the weight per unit lengthof the extruded material is varied by manually turning handle 229 whichmoves the slider on a rheostat 230 which is connected in the fieldcircuit of the generator 201. v Movement of the slider of rheostat 230varies the resistance in the field circuit 20111 of the generator 201and thereby varies the output thereof and the speed of all the conveyormotors. By watching the balance beam 26 of the weighing scale 221 andturning handle 229, the weight of the extruded material may be kept atthe proper weight.

The sliders of potentiometer 213 and rheostat 216 are connected togetherby means of a gear or chain drive 231 so that both are movedsimultaneously. If the slider of potentiometer 213 and therefore theslider of rheostat 216 are not in the center of the range there will bea voltage difference between the slider of potentiometer 213 and thecenter tap of resistor 212, inasmuch as the potentiometer 213 is nowconnected in parallel with resistor 212 and the slider of potentiometer213 is connected to the amplifier 214. This difference in voltage is fedto the amplifier 214 and as amplified is applied to the field windings20611 of Servomotor 206 to drive this motor in one direction of theother depending on the instantaneous polarity of the voltage supplied tothe winding 20651 by the amplifier 214. Winding 2061) is connectedacross 110 volt lines L-4, L-5. Servomotor 206 is connected to theslider of potentiometer 213 by means of clutch 215 and resets the sliderof potentionieter 213 to the center range to restore electrical balancebetween it and the center tap of the resistor 212. At the same time theslider of rheostat 216 is reset to the center of the range by the gearor chain drive 231, so that when switch 204 is closed to give automaticoperation, the control will have been entirely reset to center of range.

Loop or tension control Referring to Fig. l, the loop or tension controlincludes three selsyn transmitters 232, 233 and 234. Each of the selsyntransmitters is positioned at a point in the conveyor line where theextruded strip material is unsupported. Selsyn transmitter 232 ispositioned adjacent the point where the extruded material 10 leaves theconveyor 14; selsyn transmitter 233 is positioned adjacent the deliveryside of the conveyor roller 18; and selsyn transmitter 234 is positionedbetween the conveyors and 16. At each of these points the material sagsand forms a loop. The amount of sag or size of the loop is proportionalto the tension in the extruded material at that point. The larger thedepth of the loop the less the tension, and the smaller the depth of theloop the greater the tension.

The shaft of each of the selsyn transmitters has secured thereto a pairof feelers 235 which engage the extruded material4 and are held incontact therewith by the force of gravity. As the tension in theVextruded material increases or decreases and the size or depth of theloop correspondingly decreases or increases, the feelers 235 are rotatedupwardly or downwardly. The feelers 235 in turn, rotate the shaft androtor of the selsyn transmitter to which they are attached.

As will hereinafter be described in detail, the position of the rotor ofthe individual selsyn transmitters is compared electrically with theposition of the rotor of a control transformer and if they are not inelectrical alignment, a signal voltage is induced in the rotor windingof the control transformer. This signal voltage, which is thereforeproportionate to the amount of rotation of the rotor of the controlselsyn transmitter, is fed into an amplifier which in turn drives aServomotor in one direction or the other depending upon theinstantaneous polarity of the voltage.

The Servomotor moves a slider on a rheostat in each of the fieldcircuits of the conveyor motors M-2, M-3 and M-4 to increase or decreasethe speed of the individual conveyors that they drive. By a specialclutch arrangement, movement of the rotor of the first selsyntransmitter, namely, selsyn transmitter 232 will increase or decreasethe speed of conveyor motors M-2, M-3 and 1 4. Movement of the rotor ofthe second selsyn transmitter, namely, selsyn transmitter 233, willincrease or decrease the speed of conveyor motors M-3, M-4 and movementof the rotor of selsyn transmitter 234 will increase or decrease thespeed of only conveyor motor M4.

The loop control circuit is shown in detail in Fig. 6. Each of theselsyn transmitters 232, 233 and 234 are sequentially connected into thecontrol circuit by the sequential actuation of microswitches 220, 236and 237 (Fig. 5) by the cam plate 221.

Actuation of micro-switch 220 completes the circuit between lines L-4,L-11 and L-5 to energize control relay 237 and clutch operatingsolenoids 23851, 23911 and 24051.

Energization of control relay 237 closes normally opened contacts 23711,237C and opens normally closed contacts 237b and 237d. Opening ofcontacts 237b and 23751 disconnects the field windings 24111 of areference selsyn 241 from the field windings 24251 of controltransformer or selsyn receiver 24211 and closing contacts 23711 and 237Cconnects the field windings 23251 of selsyn transmitter 232 to the fieldwindings 24211 of control transformer 242.

If at this instance, the rotor of the selsyn transmitter 232 is not inelectrical alignment with the rotor of the control transformer 242,thereby indicating a variation of the tension of the extruded materialfrom the standard set by the position of the rotor of selsyn 241, asignal voltage will be induced in the rotor winding 242e of thetransformer 242. The signal voltage is fed into an arnplifier 243.Amplifier 243 is of a conventional type well known to those skilled inthe art. A simplified circuit diagram of amplifier 243 is included inFig. 6 for the purpose of illustration. As is readily apparent to oneskilled in the art, either control relay 244 or relay 245, which areconnected to the output side of the amplifier, is energized dependingupon the instantaneous polarity of the signal voltage fed into theamplifier. If the control relay 244 is energized, it closes contacts24411 to complete a circuit to energize a control relay 246.Energization of control relay 246 closes contacts 24651 to complete thefield circuit 24711 of a Servomotor 247 to drive the motor 247 in onedirection.

if control relay 245 is energized, it closes contacts 245e to complete acircuit to energize control relay 248. Energization of control relay 24Scloses contacts 24811 to complete the fieldlcircuit1247l1 of servo motor247 to drive the' motor-247 in the other direction. Both field circuits9 are energized from lines If-4 and L-5 through transformer 249.

Servomotor 247 moves the sliders on rheostats 250, 251 and 252 in thefield circuits of conveyor motors M-2, M3 and M-4 respectively through agear or chain drive 253 and clutches 238, 239 and 240. Each of theclutches, as previously described, was engaged when their respectiveoperating solenoids 23851, 239a, and 240a were energized whenmicro-switch 220 was actuated by cam plate 221. Each of the solenoids238a, 239a and 24011 are direct current operated and an appropriaterectifying circuit is provided for each solenoid, including a seleniumrectifier 253, resistor 254 and capacitor 255 for solenoid 238a;rectifier 256, resistor 257 and capacitor 258 for solenoid 239a; and arectifier 259, resistor 260 and capacitor 261 for solenoid 240e.

Movement of the sliders of the potentiometers 250, 251 and 252 increasesor decreases the resistance in the fields of each of the conveyor motorsM-2, M3 and M-4 and thereby increases or decreases the speed of themotors to correct the tension in the extruded material carried by theconveyors at the point contacted by the feelers of selsyn 232.

At the same time that servo motor 247 moves the sliders of the rheostats250, 251 and 252, it also rotates the rotor of control transformer 242in the appropriate direction by means of drive 253a until it is inelectrical alignment with the rotor of the control selsyn 232. When itreaches this position of alignment, no voltage is induced in thesecondary winding 242e and control relays 244, 245, 246, 248 aredeenergized thereby opening the contacts thereof and stopping motor 247.

When micro-Switch 220 is released, control relay 237 and all clutchsolenoids 238a, 23911 and 240a are de-energized. De-energization ofcontrol relay 237 opens contacts 237a and 237e and disconnects the fieldwinding 232e of the selsyn transmitter 232 from the field windings 242aof control transformer 242 and closes contacts 237b and 237d to connectthe field windings 241a of reference selsyn 241 to the field windings242e of the control transformer 242. Reference selsyn 241 has a fixed,but adjustable rotor which is set tovcorrespond in position to therotors of the control selsyn transmitters when the extruded material isat the desired standard tension.

When the field windings 242a of the control transformer 242 areconnected to the field windings 24111 of the reference selsyn 241, ifthe rotors of each are out of alignment electrically, a signal voltageis induced in the rotor winding 242e. This signal voltage is fed intothe amplifier 243 and motor 247 is again operated in one direction orthe other depending upon whether control relay 244 or 245 is energized.At this time, however, the sliders of the rheostats 250, 251 and 252 arenot moved by the motor 247 as clutches 238, 239 and 240 are not engaged.The rotor of the control transformer 242 is, however, rotated by thegear or chain drives 253 and 25311 until it is in electrical alignmentwith the fixed rotor of the reference selsyn 241. When the rotor of thecontrol transformer assumes electrical alignment with the rotor of thereference selsyn 241, there is no signal voltage induced in the rotorwinding 242e and control relays 244, 245, 246 and 247 are deenergizedand their respective contacts open to stop motor 247. This electricalcomparison and resetting of the control transformer takes place eachtime that one of the micro-switches 220, 236 or 237 is released andbefore the next micro-switch is actuated, so that the controltransformer is reset for the next comparison with the next controlselsyn transmitter.

When the cam plate 221 actuates switch 236, a circuit is completed fromL-4 through conductor L-12 to L-5 to energize control relays 262 and263. Energization of control relay 263 opens normally closed contacts263a to leave an open circuit to clutch solenoid 238:1 so that it willnot be energized and closes contacts 263b to complete a circuit from L-4through conductor L-12 to L-S 10 to energize clutch solenoids 23% and24051, and thereby engage clutches 23g and 244).

Energization of control reiay 262 opens contacts 262b and 262d todisconnect the field windings 241:1 of the reference selsyn 241 from thefield windings 242er of the control transformer 242, and closes contacts262a and 262C to connect the field windings 233e of control selsyn 233to the field windings 242e of the control transformer 242.

If the rotor of control selsyn transmitter 233 is out of electricalalignment with the rotor of the control transformer 242, therebyindicating a deviation in tension of the extruded material from thedesired standard, a signal Voltage is induced in the rotor windings 242eof control transformer 242. This voltage signal is fed into theamplifier 243 and in a similar manner as described in connection withcontrol selsyn transmitter 232, drives servomotor 247 in one directionor the other. Motor 247 moves the sliders of rheostats 251 and 252 toincrease or decrease the speed of conveyor motors M3 and M-4 to correctthe tension in the extruded material at the point where the feelers ofselsyn 233 contact the material. The slider of rheostat 25th is notmoved because clutch 238 is not engaged at this time.

When micro-switch 236 is released, the rotor of control transformer 242is again reset to be in electrical alignment with the stationary rotorof the reference transmitter 241 in the manner as previously described.

When micro-switch 237 is actuated, a circuit is completed from L-4through conductor L-13 to line L-5 to energize control relays 264 and265. Energization of control relay 264 opens noimally closed contacts264e: to open the circuit to clutch solenoids 238g and 239i; so thatthey will not be energized and closes normally open contacts 264b tocomplete a circuit to energize clutch solenoid 240er.

Energization of control relay 265 opens normally closed contacts 265band 2656] to disconnect the field windings 24111 of reference selsyn 241from the field windings 242:1 of control transformer 2452 and closesnormally open contacts 265g and 265i: to connect the field windings 234aof control selsyn transmitter 234 to the field windings 242a of thecontrol transformer 242. lf at this time the rotor of the control selsyntransmitter 234 is not in electiical alignment with the rotor or" thecontrol transformer 242, a signal voltage is induced in the rotorwinding 242e of the control transformer 2412. This Voltage is fed intothe amplifier 2 43 and drives servomotor 247 in the same manner aspreviously described in connection with control selsyn generator 232.Motor 247v moves the slider of rheostat 252 and thereby increases ordecreases the speed of con veyor motor M-4 to correct the tension in theextruded material at the point where trie feelers of selsyn 234 contactthe material. The sliders of rheostats 25@ and 251 are not moved asclutches 23S and 239 are not engaged at this time.

When micro-switch 237 is released, the position 0f the rotor of thecontrol transformer 242 is again cornpared with the position of thestationary rotor of the reference selsyn 241 and is reset in accordancetherewith. Micro-switch 229 is then again actuated and the cycle ofchecking the tension in the extruded material and correcting the speedof the conveyors is again repeated. In this manner the tension in theextruded material is constantly checked at 3 points along the conveyorline and corrections made in the speed of the coriveyors to maintain thedesired tension in the material as it travels along the cooling path. Ifthe control systern is set to maintain the material at substantiallyzero tension then the amount of shrinkage of the material in its travelfrom the weighing scale to any particular tension checking point will beproportioned to the difference between the speeds of the conveyoradjacent the weighing scale and the conveyor against the particularchecking point.

The rotor windings 24112, 232i), 2331) and 23412 of selsyn transmittersZai, 232, 233 and 235.L are connected across lines L-l, L- to energizerespective windings.

Scale compensator The scale compensator includes both mechanical andelectrical elements. The mecha cal elements which are best shown inFigs. 2 and 3 include the supporting rollers 31 and 32 previouslyreferred to in conjunction with the description of the continuousweighing sc l' 31 is journaled at each end *i a bracket .so and roher 32is journaled at each end a bracket 36. Bracket 35 is secured to andsuported by pair of shafts 37 and 38 and bracket 3: is secured to andsupported by a pair of shafts 39 and Each shaft slide". in identicalbearings il secured to each side ot u fil-2.

Rollers 31 and move'i toi s asvay from each other by a shaft Y ich isthreaded at each end as shown at and @ne end has a left hand thread andthe other a right hand thread. mucket 35 has secured thereto a threadedbushing i6 into which the threaded end bracket 36 has secured thereto athrea ed bu rg into uf'hch the threaded end is threaded. o shaft in onedirection or the other, therefore, moves the rollers 31 and 32 eithertowards or away Shaft d3 is rotated through bev-led gears c l i.; by amotor 266.

The distance apart .vnico e rollers 31 and 32 are set atects theposition of the oz' beam 26 of the weighing scale as it is the length ofextruded material supported between tiesc rollers which is weighed. Ifthe scale is set to bala Ace wh .n the rollers are spaced apart apredetermined distance, then if the rollers are moved apart anadditional d' tance, the balance beam 26 will move to ind :2te a l ierweight or if moved together the balance beam will move to indicate alighter weight.

The extruded material when it reaches -he s mechanism 1.. will not havetre sane wei .ht per unit of length that it had at the weighing scale.This is to shrinkage of the extruded material as it is cooled during itstravel along the c nveyor system. Thus if a linear foot o the extrudedhas a particular weight at the weighing scale s e mass of material whenit reaches the seve.f echanism will have a smalier linear measurmeent afoot or' the extruded material when it reaches the severing mechanismwill necessarily have a greater v-.feight than a linear foot ot thematerial at the iveig" scaie. This diiierence in weight of the extrudedmater'ai will therefore he proportioual to the percentage of s okage. itthe per cent of shrinkage is known, a compensating correction can beintroduced into the weig c by varying the distance between the ro' s olo 32 so that the scale will balance when the wei ht of the extrudedmaterial is of the desired standard it roaches the severing mechanism.Because or the unpredictable nature of plastic materials and inparticular r hoer, it is impossible to predict accurately the percentageof shrinkage.

As previously described conjunction with the loop or tension control,it` the tension control is set to maintain substantially zero tension inthe extruded material, then the ,ercentage of shrinkage of the materialin its travel from the weighing sc e to any particular tension checkingpoint will be proportional to the difference between the speeds of thecor eyor adjacent the weighing scale and the conveyor adjacent theparticular checking point. Thus the total percentage shrii age of thematerial in its travel from the weighing scale to the severing mechanismwill be proportional to the difference in speeds between the conveyoradjacent the weighing scale and the conveyor adjacent the last checkingpoint which delivers the matcriai to the severing mechanism. As was alsoexplained previously, the change in weight per unit of length is alsoproportional to the percentage of Etf.

shrinkage. Thus in correlating these facts, the change in weight perunit of length of the material in its travel from the weighing scale tothe severing mechanism will be proportional to the difference in speedsof the conveyor i3 adjacent to the weighing scale 21 and the conveyor 16adjacent to the severing mechanism 12.

The scale compensator utilizes this diierence in speeds to provide acompensating error in the weighing scale so that the weight of theextruded material will be of the desired standard weight per unit oflength when it reaches the severing mechanism.

In utilizing this dilerence in speeds of the two conveyors, twotachometer generators 267 and 268 (Figs. 1 and 5) having field windings267a and 267b are provided, the rst being driven from the irst conveyor13, the second being driven from the last conveyor 16. T he twotachometer generators are connected together electrically so that theresultant voltage of the two will be proportional to the difference inspeed between the first and last conveyors and therefore the percentageof shrinkage in the extruded material in its movement from the first tothe last conveyor. This voltage is amplified and is used to control theoperation of motor 266 which varies the distance between the rollers 31and 32 to cornpensate for the change in weight due to shrinkage. lf therollers are moved apart, the balance beam 26 moves downwardly and at thesame time moves the iron core 33 of the transformer 34 in a direction toinitiate the weight control circuit to increase the speed of all theconveyor motors to thereby decrease the weight per unit length of theextruded material.

As can be seen by reference to Fig. 5, which discloses the details ofthe control circuit, the output of tachometcr generator 267 is connectedin parallel with a resistor 269 and tachorneter 268 is connected inparallel with potentiometer 270. The slider 27061 of potentiometer 270is connected to an amplifier 271 which is identical with the amplifier214 of the weight control circuit and resistor 269 has a center tapconnection with the amplifier 271. lf the voltage generated bytachorneter 268 is smaller than that generated by tachometer 267, thenthere will be a voltage diierence between the slider of potentiometer270. and the center tap of resistor 269, assuming that the slider ofpotentiometer 276 is at the center of the range. This voltagedifference, which will be proportional to the shrinkage in the extrudedmaterial, is fed into the amplifier 271 and is amplified and applied tothe field winding 272a of a servomotor 272 to drive this motor in onedirection or the other depending upon the instantaneous polarity of thevoltage. Field winding 27211 of servomotor 272 is connected across voltlines L-4, L-S. Motor 272 moves the slider of potentiometer 270 untilelectrical balance is reached between it and the center tap of theresistor 269.

At the same time servomotor 272 drives a selsyn transmitter 273 throughreduction gearing 274. The field winding 2730 of selsyn transmitter 273is connected to the field windings 275:1 of a control transformer 275.If the rotor of the control transformer is not in the same electricalposition as the rotor of the selsyn transmitter, a voltage signal willbe induced in the rotor windings 275b of the control transformer. rhisvoltage signal is fed into an amplifier 276, identical to the amplifier243 of the loop control circuit, which energizes either of two controlrelays 277 or 278 depending upon the instantaneous polarity of the inputsignal. The polarity is determined by the direction in which the rotorof selsyn 273 and the slider 270:1 have moved.

If Control relay 277 is energized, it closes contacts 277u and openscontacts 277]; to complete a circuit to energize a control relay 279.Energization of control relay 279 closes normally open contacts 279:1,27% and 279C, to connect motor 266 with a 440 volt source (not shown) todrive the motor 266 in one direction. Operation of motor 266 moves therollers31 and 32 to provide a com- 13 pensating error in the weighingscale 21 as previously described,

If control relay 278 is energized it closes contacts 27851. and openscontact 27811 to complete a circuit to energize the control relay 280.Energization of control relay 28@ closes normally open contacts 280a,2S0b and Ztic to connect the motor 266 to a 440 volt power source todrive the motor in the opposite direction from that which resulted inclosing contact 279a, 279b and 279e. Gperation of the motor 266 in thisdirection moves the rollers 31 and 32 in the opposite direction toprovide a compensating error in the scale 21.

When this compensating error is introduced into the weighing scale, thebalance beam moves off balance and the speed of the conveyor motors arevaried by the weight control circuit to correct the weight of theeXtruder material to bring the balance beam back into balance.

As the motor 266 rotates to move the rollers 31 and 32, it also movesthrough gearing 281 the rotor of the control transformer 275. When therotor of the transformer reaches the electrical position correspondingto the position of the rotor of the selsyn transmitter 273, there is novoltage induced in the rotor winding 275b of the control transformer andtherefore no voltage signal is fed to the amplifier 276. The controlrelays 278 and 277 are therefore de-energized, thereby opening contacts277b and 278b and closing contacts 277e and 278C: to stop the motor 266.

lf the percentage shrinkage again changes and this change is reflectedby a new difference in the voltage output between the two tachornetergenerators, another cycle of weight correction will occur.

In this manner, the weight compensating system, continuously checks theshrinkage and introduces a compensating error in the weighing scalewhich in turn initiates the weight control circuit to vary the speed ofall the conveyors to vary the weight of the extruded material.

A control relay 282 is connected across lines L-S, L-l, and which,therefore, is energized only when microswitch 220 is actuated by the camplate 221. Energization of control relay 282 by the actuation or"microswitch 220 opens contacts 282a. Opening of contacts 28211 breaksthe circuit to control relays 279 and 266 and thereby prevents operationof rnotor 266 while microswitch 220 is actuated.

Inasmuch as the weight control system operates only when micro-switch220 is actuated, the opening of contacts 282:1 by actuation ofmicro-switch 220 will prevent motor 266 from moving the rollers 31 and32 to make a correction in the weighing scale 21 while the weightcontrol system is correcting the speed of the conveyors. By preventingthe weight control system and the scale compensating system from beingoperated simultaneously, hunting by the motor 266 is prevented.

Modification for using A. C. motors If it is desired to operate thevarious conveyors by A. C. constant speed motors, rather than by D. C.motors, the same control circuit with slight modifications may be used.In such a modification it is necessary to use some type of variablespeed drive between the A. C. motors and the conveyors. One type ofvariable speed drive that may be used, is what is commonly known as aReeves drive. Such a drive is shown in Fig. 7.

Referring to Fig. 7, there is shown a conventional Reeves driveincluding a variable pitch pulley sheave S which is driven by an A. C.constant speed motor M', a driving belt 51, and a variable pitch pulleysheave S2, which drives output shaft 53. The pitch of the sheaves 50 and52 and therefore the speed ratio is varied by changing the spacingbetween their individual tapered flanges which are slidably mounted ontheir respective shafts. The spacing is varied by actuating links and 55which are pivotally mounted intermediate their lengths at 56 and 57 andare pivotally connected to the anges of the sheaves. By pivoting thelinks toward or away from each other the anges on one sheave will bemoved in one direction while the flanges on the other sheave will bemoved in the other direction, thereby changing the speed ratio betweenthe motor M and the output shaft 53. The links 54 and 55 are actuated bya threaded shaft SS which has two threaded portions S9 and 66, one righthand and one left hand. The threaded portions 59 and 6d are threadedinto threaded nuts 61 and 62, pivotally connected to the ends of thelinks 54 and 55. Rotation of shaft 53, therefore, moves the actuatinglinks 54 and to vary the pitch of the sheaves and therefore the speedratio.

in utilizing such a variable speed drive in the present invention, an A.C. constant speed motor and a variable speed drive of the type abovedescribed is substituted for D. C. motor M-i.. The generator 261 iseliminated as well as rheostats 216, 250, 251 and 252. A variable speeddrive is also substituted for each of the motors lvl-2, lvl-3 and lvl-4.The A. C. constant speed motor is connectcd to the input shaft of thefirst variable speed drive and the output shaft of the same drive isconnected to the input shafts of the subsequent Reeves drives. Theoutput shaft of each of the Reeves drives is connected to one of theconveyors and the shafts which originally moved the sliders on therehostats 216, 250, 251 and 252 are connected to the threaded actuatingshaft 53 of the variable speed drives.

Such a substitution is shown in Fig. 8 in which an A. C. motor M-1' issubstituted for the D. C. motor lvl-1. The A. C. motor M-l is connectedto the input shaft 65a of a Reeves drive 65. The output shaft 65h isconnected to the input shafts 66a, 67a and 68a of similar Reeves drives66, 67 and 68 respectively by means of a chain drive 69. By connectingthe output shafts 65b, 661'), 67b and 63]: respectively to conveyors 13,18, 15 and 16, the speeds of these conveyors can be changedsimultaneously by operation of the threaded actuating shaft 65C of theReeves drive 65. Actuating shaft 65C is operated by the servo motor 707of the weight control circuit which originally moved the slider of therheostat 216 in the weight control circuit using D. C. motors. In thismanner the speeds of all the conveyors are increased or decreased inaccordance with a weight deviation in the extruded stock from standard,to thereby correct the weight.

The actuating shafts 66e, 67e and 68e of the Reeves drives 66, 67 and 68are rotated selectively by servornotor 247 through clutches 238e, 239eand 24961 and chain drive 253 in the same manner that the sliders ofrheostats 25d, 251 and 252 in the tension control circuit were moved, tothereby vary the speed ratio of the output shafts of the Reeves drives66, 67 and 63 and therefore the speeds of the individual conveyorsdriven thereby to correct the tension in the extruded material.

The modified control system as above described otherwise operates thesame as the D. C. conveyor motor systern.

Modicatz'on of the loop or tension control circuit Referring to Fig. 9,there is shown a modification of the loop or tension control circuit.According to this modification there is provided an independent,duplicate control circuit for each of the control selsyn transmitters232, 233 and 234 so that each control selsyn controls the speed of onlyone conveyor motor. This is in contrast to the integrated controlcircuit of Fig. 6 which as previously described will vary the speed ofall or less than all of the conveyor motors simultaneously dependingupon which of the control selsyn transmitters is energized.

in Fig. 9, there is shown the modified circuit for only control selsyn232. The circuits for control selsyns 233 and 234 are merely duplicatesof this circuit, so a description of the circuit for control selsyn 2232will sufce for all.

The circuit of Fig. 9 is essentially the same as that of Fig. 6 exceptthat the control selsyns 233 and 234, rheostats 2.5i and 2552, clutchsolenoids 239A and 246A and the inter-connecting solenoid operatedswitches have been eliminated. The same reference numerals have beenused to identify the same elements in Figs. 6 and 9. This circuitfunctions in the same manner as the circuit of Fig. 6 to vary the speedof only conveyor motor M-Z when a change of tension occurs in theextruded material as it leaves the conveyor 14. The speeds of conveyormotors lvl-3 and M-d are not varied by this circuit because theirinter-connecting switches have been eliminated.

The circuit of Fig. 9 is connected across microswitch 22C* (Fig. 5) andis energized each time that microswitch 22d is closed by cam 212i.Duplicate circuits (not shown) are connected across microswitches 236and 237 to vary the speeds oi conveyor motors M-3 and M-d. In thismanner duplicate but independent tension control circuits for each ofthe conveyor motors M-Z, lvl-3 and M- are sequentially energized as themicroswitches 22%, 236 and 237 are sequentially actuated by the cam 221to correct the tension in the extruded material at a plurality ot pointsalon7 the conveyor series.

The advantages of having duplicate independent circuits for each ot thecontrol selsyns as shown in Fig. 9 rather than the integrated circuit ofFig. 6 are simplicity and ease or` replacement.

Conclusion While the above control system has been described in terms ofits comportent parts, viz., the weight control system, the loop ortension control system, and the scale compensating system, it canreadily be seen that these component parts form an integrated controlsystem.

The scale compensating system depends on the loop or tension controlsystem to maintain the individual conveyors at the proper speeds tomaintain the extruded material at substantially zero tension, so thatthe difference in speed between the irst and last conveyors will beproportional to the change in length due to shrinkage or stretching or"the extruded material.

The scale compensator is integrated with the weight control system tointroduce a compensating error therein, so that it will correct or varythe weight of the extruded material.

The inte .u control system accurately controls the extruded material, sothat material as delivered at the end of the conveyor system will havesubstantially no tension and will oe of a predetermined weight per unitof length. Tne control system may be used in any plastic extruding :.1where it is desired to control the weight and tension in the extrudedmaterial. The control system, is particularly useful in the extrusion ofrubber, commonly known as tubing lt is to be understood that the abovedescription and accompanying drawings is for the purpose of illustrationonly and not by the way of limitation and changes and modifications maybe made therein without departing from the spirit and the scope of theinvention.

Having thus described our invention, what we claim and desire to protectby Letters Eatcnt is:

l. ln a conveyor system for conveying continuously extruded material,from extruding die, said conveyor system having a ies of individualconveyors and means for independently driving each conveyor, a controlsystem comprising, means adjacent the extruding die for detecting aweight deviation in the extruded material from a predetermined standard,control means operated by weight deviation detecting means forsimultaneously varytne speeds of all the conveyor driving means tocorrect the weight ct the extruded material, means adjacent theconveyors at a plurality of points along the convey r system fordetecting a tension deviation in the extruded material, control meansoperated by said tension deviation iii) detecting means for varying thespeed of the individual conveyor driving means as necessary to correctthe tension and means responsive to the difference in speed of the tirstand last conveyors inthe series for introducing a comnsating correctionin the second named means to com- "tte for the changes in weight perunit of length of extruded material due to shrinkage in its travel alongthe conveyor system.

2. ln a conveyor system for conveying continuously exffu led materialfrom an extruding die, -said conveyor sysi having a series of spacedindividual conveyors and means for independently driving each conveyor,a control system comprising, means positioned at a point adjacent theextruding die for supporting a predetermined length ci the extrudedmaterial, said means being movable in response to a deviation in weightof the extruded material from a predetermined standard, control meansresponsive to movement of said supporting means for simultaneouslyvarying the speed of all the conveyor driving ine-ans to correct theweight of the extruded material, movable means engaging the material ata plurality of positions along the conveyor system where the material isunsupported between the individual spaced conveyors, control meansresponsive to the movement of said movable ension, and means responsiveto the difference in speed ci. the rst and last conveyors in theconveyor series for varying the length of extruded material supported bysaid supporting means whereby a compensating correction is introduced insaid first named control means to vary the eds of the conveyor drivingmeans to change the weight extruded material to compensate for thechange in weight due to shrinkage in the material during the travelalong the conveyor system.

3. in a conveyor system for conveying continuously extruded materialfrom an extruding die, said conveyor m having a series of spacedconveyors and means for ving the individual conveyors, a control systemcomprising, adjustable spaced supporting means, means adiacent theextruding die for weighing the length of extruded material supportedbetween said spaced supportmeans including means movable in response toand proportionate to a deviation in weight of the extruded material froma predetermined standard weight, control ieans responsive to themovement of said movable means to vary the speed of the conveyor drivingmeans to correct the weight of the extruded material, means forconstantly engaging the extruded material at a plurality 'of pointswhere the material sags between the conveyors, and movable in responseto a change in the depth of sag occasioned by a change in tension in thematerial, control means responsive to the movement from a predeterminedposition of said means for engaging the extruded material to in creasethe speed of the individual conveyor driving means to vary the tensionin the material and therefore the depth ot sag which said movable meansare moved back to said predetermined position, and means responsive tothe ditl'erence in speed of the first and last conveyors in the conveyorseries for varying the spacing between said supporting means to therebyvary the length `of material weighed by said weighing means 'whereby acompensating correction is introduced into said Weighing means tocompensate for the change in weight in the material due to shrinkage.

4. in a conveyor system for conveying continuously extruded materialfrom an extruding die said conveyor system having a series ofindividual, spaced conveyors and means for independently driving theindividual conveyors,

control system comprising, spaced supporting means positioned adjacentsaid extruding die, a weighing scale for continuously weighing extrudedmaterial supported between said spaced supporting means, said weighingscale having balance beam, control means'responsive to movement of thebalance beam for varying the speed of all the conveyor driving means,feeler arms for engaging the extruded material at the points where thematerial sags between the lspaced conveyors, said feeler arms beingmovable in response to a change in the depth of sag occasioned by achange of tension in the material, control means responsive to themovement of the feeler arms from a predetermined point for varying thespeed of the individual conveyors to vary the tension in the extrudedmaterial and return the feeler arms to said predetermined point, andmeans responsive to the difference in speed of the iirst and lastconveyor driving means for varying the spacing between said spacedsupporting means to vary the length of the extruded material weighed bysaid weighing means to thereby introduce a compensating correction insaid weighing means to compensate for the change in weight due toshrinkage of the extruded material in its travel along the conveyorseries.

5. in a conveyor system for conveying continuously extruded materialfrom an extruding die, said conveyor system having a series of spacedconveyors and means for driving each of said conveyors, a control systemcomprising means for continuously weighing a. predetermined length ofextruded material and varying the speed of all the conveyor drivingmeans when the weight of the extruded material varies from apredetermined standard weight, individual means positioned at aplurality of points along the conveyor series and movable in response toa change in depth of the sag of the extruded material at the spacesbetween the conveyors, control means associated with each of saidindividual means, means for sequentially actuating each of said controlmeans, said control means serving to vary the speed of all conveyordriving means of the individual conveyors more remote from the extrudingdie than the individual means that the control means is associated withand in proportion to the movement of the individual means, and meansresponsive to the diiierence in speed of the tirst and last conveyors inthe series for introducing a compensating correction in said weighingmeans to compensate for the change in weight due to shrinkage of theextruded material.

6. In a conveyor system for conveying continuously extruded materialfrom an extruding die, said conveyor system having a series of spacedindividual conveyors and means for independently driving each conveyor,a control system comprising, spaced supporting means adjacent theextruding die, a weighing scale for weighing a length of extrudedmaterial supported between said supporting means, said weighing scalehaving a balance beam, a differential transformer, a movable iron corefor the transformer, said core being attached to said balance beam andmovable thereby whereby a signal voltage will be introduced in thesecondary windings of the transformer proportionate to the amount ofmovement of the iron core, control means responsive to said signalvoltage to vary the speed of all the conveyor driving means, detectingmeans positioned at a plurality of points along the conveyor system fordetecting a change in tension of the extruded material from apredetermined standard, control means associated with said detectingmeans for varying the speed of the individual conveyors to maintain apredetermined standard tension along the length of the material, andmeans responsive to the diterence in speed between the first and lastconveyors for varying the spacing of said spaced supporting means tointroduce a compensating correction in the weighing scale to therebycompensate for changes in weight due to shrinkage of the extrudedmaterial.

7. ln a conveyor system for conveying continuously extruded materialfrom an extruding die, said conveyor system having a series ofindividual, spaced conveyors, and means for independently driving eachconveyor, a control system comprising, adjustable, spaced supportingmeans positioned adjacent the extruding die, a weighing scale forweighing a length of the extruded material supported between said spacedsupporting means, said weighing scale having a balance beam, adifferential transformer, said transformer having two secondarywindings, a resistor connected across one of said windings, apotentiometer connected acrosslthe other oi said windings, a center tapfor said resistor, a slider for said potentiometer, a movable iron corefor said transformer, said core being attached to said balance beam andmovable therewith whereby a signal voltage will exist between saidcenter tap and said slider proportional to the amount of movement ofsaid iron core, means including a servomotor operated by said voltagesignal, said slider being con nected to said servomotor and movedthereby until the voltage between the slider and said center tap iszero, means actuated by said servomotor to vary the speed of all theconveyor driving means, and means for disconnecting said servomotor fromsaid means for varying the speed of the conveyor driving means and forresetting the slider of the potentiometer to the center of the range ofthe potentiometer, detecting means positioned at a plurality of pointsalong the conveyor system for detecting a change in tension in theextruded material, control means associated with said detecting meansfor varying the speeds of the individual conveyors to maintain apredetermined standard tension along the length of the material, andmeans responsive to the dilierence in Speed between the first and lastconveyors for varying the spacing between said supporting means tointroduce a compensating error in the weighing scale to therebycompensate for changes in weight due to shrinkage ot the extrudedmaterial.

8. in a conveyor system for conveying continuously extruded materialfrom an extruding die, said conveyor system having a series ofindividual, spaced conveyors, and means for independently driving eachconveyor, a control system comprising, spaced supporting means adjacentthe extruding die, a weighing scale for weighing a length of theextruded material supported between said spaced supporting means, saidweighing scale having a balance beam, a differential transformer, saidtransformer having two secondary windings, a resistor connected acrossone of said windings, a potentiometer connected across the other of saidwindings, a center tap for said resistor, a slider for saidpotentiometer, a movable iron core for said transformer, said iron corebeing attached to said balance beam and movable therewith whereby asignal voltage will exist between said center tap and said sliderproportional to the amount of movement of said iron core, meansincluding a servomotor operated by said voltage signal, said sliderbeing connected to said servomotor and moved thereby until the voltagebetween the slider and said center tap is zero, means actuated by saidservomotor to vary the speeds of all the conveyor driving means, meansfor periodically disconnecting said servomotor from said means forvarying the speeds of the conveyor driving means and for disconnectingsaid potentiometer from across said second named transformer winding andconnecting said potentiometer across the iirst named winding whereby avoltage signal will again exist between said slider and said center tapand said servomotor will be driven therebyto reset the slider to thecenter of the range of the potentiometer so that there will be zerovoltage between the slider and the center tap, detecting meanspositioned at a plurality of points along the conveyor system fordetecting a change in tension in the extruded material, control meansassociated with said detecting means for varying the speeds of theindividual conveyors to maintain a predetermined standard tension, andmeans responsive to the difference in speed between the rst and lastconveyors for varying the spacing between said supporting means tointroduce a compensating correction in the weighing scale to therebycompensate for changes in weight due to shrinkage of the extrudedmaterial.

9. In a conveyor system for conveying continuously extruded materialfrom an extruding die, said conveyor system having a series ofindividual spaced conveyors and individual driving means forindependently driving each conveyor, a control system comprising, meansresponsive to a change in weight per unit of length of the extrudedmaterial from a predetermined standard for simultaneously varying thespeed of all the conveyor driving means to correct the weight of theextruded material, means for detecting a variation in the tension in theextruded material at a plurality of points along the conveyor series andfor varying the speed of tae individual conveyor drivingy means tocorrect the tension, said tension detecting means including feeler armsfor engaging the extruded material at points where the material sagsbetween the spaced conveyors, a selsyn transmitter for each of saidfeeler arms, each of said feeler arms being connected to the rotor ofone of said selsyn transmitters whereby the rotor will be rotated bysaid feeler arm when said feeler arm is moved from a predeterminedposition in response to a change in depth of sag occasioned by a changein tension in the material, control means responsive to the movement ofsaid selsyn transmitter rotor to vary the speed of the individualdriving means to correct the tension in the material and meansresponsive to a difference in speed in the first and last conveyors inthe conveyor series for introducingJ` a compensating error in the secondnamed means responsive to a change in weight to thereby simultaneouslyvary the speed of all the conveyor driving means whereby the materialwhen delivered at the end of a conveyor system will be of apredetermined standard weight per unit of length.

10. In a conveyor system for conveying continuously extruded materialfrom an extruding die, said conveyor system having a series ofindividual conveyors and means for independently driving each conveyor,a control systern comprising, adjustable, spaced supporting means, meansadjacent the extruding die for weighing the length of extruded materialsupported between said supporting means, control means actuated by saidweighing means to vary the speed of all the conveyor driving means,means adjacent the conveyors at a plurality of points along the conveyorsystem for detecting tension deviations in the extruded material,control means operated by said tension deviation detecting means forvarying the speed of the individual conveyor driving means as necessaryto t correct the tension along the length of the material and meansincluding a tachometer generator connected to the first conveyor in theconveyor series, a tachometer generator connected to the last conveyorin the conveyor series, means for varying the spacing between said spacesupporting means, means responsive to the difference in output of saidtachometer generators to actuate said means for varying the spacingbetween said spaced supporting means whereby a compensating correctionwill be introduced in said weighing means to compensate for changes inweight due to shrinkage in the extruded material.

l1. In a conveyor system for conveying continuously extruded materialfrom an extruding die, said conveying system having a series ofindividual, spaced, conveyors and means for independently driving eachconveyor, a control system comprising, adjustable spaced supportingmeans, means adjacent the extruding die for weighing the length ofextruded mate ial supported between said supporting means, control meansactuated by said weighing means for varying the speed of all theconveyor driving means when the weight of the extruded material deviates from a predetermined standard, means adjacent the conveyors at aplurality of points along the conveyor system for detecting a tensiondeviation in the extruded material, control means operated by saidtension devia* tion detecting means for varying the speed of theindividual conveyor driving means as necessary to correct the tension,means including a tachometer generator driven by the iirst conveyor inthe conveyor series, a

tachometer generator driven by the l'ist conveyor in said conveyorseries, the output of one tachometer generator being connected across aresistor, the output of the other tachometer generator einn connectedacross a potentiometer, a center tap for the resistor, a slider for thepotentiometer, means including a servomotor operated by the existence ofa voltage difference between said center tap and said slider, saidslider being connected to said servomotor and driven thereby to move theslider until the voltage difference between said slider and said centertap zero, and means operated by said servomotor for varying the spacingbetween said supporting means to introduce a compensating error in saidweighing means to compensate for changes in weight due to shrinkage ofthe extruded material.

l2. in a conveyor system for conveying continuously xtruded materialfrom an extruding die, said conveyor system having a series of spacedindividual conveyors, and means for independently driving each conveyor,a control system comprising, adjustable spaced supporting means adjacentsaid extruding die, weighing means for continueusly weighing theextruded material supported between said space supporting means, controlmeans actuated by said weighing means for varying the speed of all theconveyor driving means when t'ne weight of the extruded material variesfrom a predetermined standard, detecting means adjacent the conveyors ata plurality of points along the conveyor system for detecting tensiondeviations in the extruded material, control means operated by saidtension deviation detecting means for varying the speed of theindividual conveyor driving means as necessary to correct the tension,means including a tachometer generator driven by the first conveyor insaid conveyor series, a tachometer generator driven by the last conveyorin said conveyor series, the output of one tachorneter generator beingconnected across a resistor, the output of the other tachometergenerator being connected across a potentiometer, a center tap for theresistor, a slider for the potentiometer, means including a servomotoroperated by the existence of a voltage difference between said centertap and said slider, said slider being connected to said servomotor anddriven thereby to move the slider until the voltage difference betweensaid slider and said center tap is zero, a selsyn transmitter, the rotorof said selsyn transmitter being connected to said servomotor and driventhereby, a control transformer, the field windings of said servomotorbeing connected to the field windings of said selsyn transmitter,whereby a signal voltage will be induced in the rotor windings of thecontrol transformer when the rotor of the selsyn transmitter is movedout of electrical alignment with the rotor of the control transformer,means actuated by the signal voltage to vary the spacing between thespaced supporting means to introduce a compensating error in theweighing means, and for moving the rotor of the control transformer intoelectrical alignment with said rotor of said selsyn transmitter so thatno voltage signal is induced in the rotor windings of the controltransformer.

13. In a conveyor system for conveying continuously extruded materialfrom an extruding die, said conveyor system having a series ofindividual spaced conveyors and means for independently driving eachconveyor, a control system comprising, means for detecting variations inthe tension in the extruded material at a plurality of points along theconveyor series and for varying the speeds of the individual conveyordriving means to correct the tension, said tension detecting meansincluding feeler arms for engaging the extruded material at points wherethe material sags between the spaced conveyors, each of said feeler armsbeing connected to the rotor of a selsyn transmitter whereby the rotorwill be rotated by said feeler arm when said feeler arm moves from apredetermined position in response to a change in depth of sagoccasioned by a change in tension in the material, means forsequentially connecting the eld windings of each of said selsyntransmitters to the iield windings of a control transformer whereby asignal voltage will be induced in the rotor windings of the controltransformer, means including a servomotor operated by said signalvoltage, means actuated by said servomotor for varying the speeds of theconveyor driving means of all the conveyors more remote from saidextruding die than said feeler arm connected to the rotor of the selsyntransmitter the iield windings of which are connected to the eldwindings of the control transformer, the rotor of said controltransformer being connected to said servo motor and driven thereby untilthe rotor is in electrical alignment with the rotor of the selsyntransmitter to which it is connected, means for periodicallydisconnecting the windings of the control transformer from the fieldwindings of each of the selsyn transmitters and connecting the windingsof the control transformer with the windings of a reference stationaryrotor selsyn transmitter and for disconnecting the servomotor from saidmeans for varying the speeds of the individual conveyor driving meanswhereby said servomotor will reset the rotor of the control transformerto be in electrical alignment with the rotor of said reference selsyntransmitter prior to the connection of the eld windings of another ofsaid selsyn transmitters to said control transformer.

14. In a conveyor system for conveying continuously extruded materialfrom an extruding die, said conveyor system having a series ofindividual conveyors and means for independently driving each conveyor,a control system comprising, adjustable, spaced supporting means, meansadjacent the extruding die for weighing the extruded material supportedbetween said supporting means, control means actuated by said weighingmeans to vary the speed of all the conveyor driving means, meansincluding a tachometer generator connected to the irst conveyor in theconveyor series, a tachometer generator connected to the last conveyorin the conveyor series, means for varying the spacing between said spacesupporting means, and means responsive to the difference in output ofsaid tachometer generators to actuate said means for varying the spacingbetween said spaced supporting means whereby a compensating correctionwill be introduced in said weighing means to compensate for change inthe weight due to shrinkage in the extruded material.

15. In a conveyor system for conveying continuously extruded materialfrom an extruding die, said conveying system having a series ofindividual conveyors and means for independently driving each conveyor,a control system comprising, adjustable, spaced supporting means, meansadjacent the extruding die for weighing the length of extruded materialsupported between said supporting means, control means actuated by saidweighing means for varying the speed of all the conveyor driving meanswhen the weight of the extruded material deviates from a predeterminedstandard, means including a tachometer generator Idriven by the firstconveyor in the conveyor series, a tachometer generator driven by thelast conveyor in said conveyor series, the output of one tachometergenerator being connected across a resistor, the output of the othertachometer generator being connected across a potentiometer, a centertap for the resistor, a sliderfor the potentiometer, means including aservomotor operated by the existence of a voltage dilerence between saidcenter tap and said slider, said slider being connected to saidservomotor and driven thereby to move the slider until the voltagedifference between said slider and said center tap is zero and meansoperated by said servomotor for varying the spacing between saidsupporting means to introduce a compensating error in said Weighingmeans to compensate for changes in weight due to shrinkage of theextruded material.

16. In a conveyor system for conveying continuously extruded materialfrom an extruding die, said conveyor system having a series of spacedindividual conveyors, and means for independently driving each conveyor,a

control system comprising, adjustable spaced'supportng means adjacentsaid extruding die, weighing means for continuously weighing theextruded material supported between said spaced supporting means,control means actuated by said weighing means for varying the speed ofall the conveyor driving means when the weight of extruded materialvaries from a predetermined standard, means including a tachometergenerator driven by the first conveyor in said conveyor series, atachometer generator driven by the last conveyor in said conveyorseries, the output of one tachometer generator being connected across aresistor, the output of the other tachometer generator being connectedacross a potentiometer, a center tap for the resistor, a slider for thepotentiometer, means including a servomotor operated by the existence ofa voltage difference between said center tap and said slider, saidslider being connected to said servomotor and driven thereby to move theslider until the voltage difference between said slider and said centertap is zero, a selsyn transmitter, the rotor of said selsyn transmitterbeing connected to said servomotor and driven thereby, a controltransformer, the eld windings of said servomotor being connected to theiield windings of/said selsyn transmitter whereby a signal voltage willbe induced in the rotor windings of the control transformer when therotor of the selsyn transmitter is moved out of electrical alignmentwith the rotor of the control transformer, means actuated by the signalvoltage to vary the spacing between the space supporting means tointroduce a compensating error in the weighing means and for moving therotor of the control transformer into electrical alignment with saidrotor of said selsyn transmitter so that no Voltage signal is introducedin the rotor winding of the control transformer.

17. ln a conveyor system for conveying continuously extruded materialfrom an extruding die, said conveying system having a series of spacedconveyors and means for driving the individual conveyors, a controlsystem comprising, adjustable spaced supporting means, means adjacentthe extruding die for weighing the length of extruded material supportedbetween said spaced supporting means, control means actuated by saidweighing means for varying the speed of all the individual conveyordriving means, and means responsive to the difference in speed betweenthe iirst and last conveyors in the conveyor series for varying thespacing between said supporting means to thereby vary the length ofmaterial weighed by said weighing means whereby a compensatingcorrection is introduced into said weighing means to cornpensate for thechange in weight in the material due to shrinkage.

18. In a conveyor system for conveying continuously extruded materialfrom an extruding die, said conveyor system having a series ofindividual conveyors and individual conveyor driving means forindependently driving each conveyor, a control system comprising, meansadjacent the conveyors at a plurality of points along the conveyorsystem for detecting a tension deviation in the extruded material,control means operated by said tension deviation detecting means forvarying the speed of the individual conveyor driving means as necessaryto correct the tension and means responsive to the difference in speedof the iirst and last conveyors in the conveyor series for varying thespeed of all the conveyor driving means simultaneously.

19. In a conveyor system for conveying continuously extruded materialfrom an extruding die, said conveyor system having a series ofindividual conveyors and individual conveyor driving means forindependently driving each conveyor, a control system comprising meansresponsive to a change in tension of the extruded material from apredetermined standard for varying the speed of the individual conveyordriving means as necessary to correct the tension in the extrudedmaterial and control means responsive to the difference in speed of theiirst and last conveyor in the series for simultaneously varying the'speed of all the conveyor driving means whereby the material whendelivered at the end of the conveyor system will be of a predeterminedstandard weight per unit of length.

20. In a conveyor system for conveying continuously extruded materialfrom an extruding die, said conveyor system having a series ofindividual spaced conveyors and means for independently driving theindividual conveyors, a control system comprising feeler arms forengaging the extruded material at the points where the material sagsbetween the spaced conveyors, said feeler arms being movable in responseto a change in the depth of sag occasioned by a change of tension in thematerial, control means responsive to the movement of the feeler armsfrom a predetermined point for varying the speed of the individualconveyors to vary the tension in the extruded material and return thefeeler arms to said predetermined point, and means responsive to thedilerence in speed between the rst and last conveyors in the conveyorseries for varying the speeds of all the conveyor driving meanssimultaneously whereby the material when delivered at the end of theconveyor system will be of a predetermined standard weight per unit oflength.

References Cited in the tile of this patent UNITED STATES PATENTS

1. IN A CONVEYOR SYSTEM FOR CONVEYING CONTINUOUSLY EXTRUDED MATERIALFROM AN EXTRUDING DIE, SAID CONVEYOR SYSTEM HAVING A SERIES OFINDIVIDUAL CONVEYORS AND MEANS FOR INDEPENDENTLY DRIVING EACH CONVEYOR,A CONTROL SYSTEM COMPRISING, MEANS ADJACENT THE EXTRUDING DIE FORDETECTING A WEIGHT DEVIATION IN THE EXTRUDED MATERIAL FROM APREDETERMINED STANDARD, CONTROL MEANS OPERATED BY SAID WEIGHT DEVIATIONDETECTING MEANS FOR SIMULTANEOUSLY VARYINT THE SPEEDS OF ALL THECONVEYOR DRIVING MEANS TO CORRECT THE WEIGHT OF THE EXTRUDED MATERIAL,MEANS ADJACENT THE CONVEYORS AT A PLURALITY OF POINTS ALONG THE CONVEYORSYSTEM FOR DETECTING A TENSION DEVIATION IN THE EXTRUDED MATERIAL,CONTROL MEANS OPERATED BY SAID TENSION DEVIATION DETECTING MEANS FORVARYING THE SPEED OF THE INDIVIDUAL CONVEYOR DRIVING MEANS AS NECESSARYTO CORRECT THE TENSION AND MEANS RESPONSIVE TO THE DIFFERENCE IN SPEEDOF THE FIRST AND LAST CONVEYORS IN THE SERIES FOR INTRODUCING ACOMPENSATING CORRECTION IN THE SECOND NAMED MEANS TO COMPENSATE FOR THECHANGES IN WEIGHT PER UNIT OF LENGTH OF EXTRUDED MATERIAL DUE TOSHRINKAGE IN ITS TRAVEL ALONG THE CONVEYOR SYSTEM.